Heterotrimeric GTP-binding proteins comprised of Gα, Gβ and Gγ subunits are key regulators of a multitude of signaling pathways in eukaryotes. In plants, G-proteins are currently a focus of intense research due to their involvement in modulation of many agronomically important traits such as seed yield, organ size, abscisic acid (ABA)-dependent signaling and stress responses, plant defense responses, symbiosis and nitrogen use efficiency. The mechanistic details of G-protein biochemistry in modulating these processes in plants remain largely unknown. Although the core G-protein components and their activation/deactivation chemistries are broadly conserved throughout eukaryotic evolution, their regulation seems to have been rewired in plants to meet specific needs. Plant G-proteins may be spontaneously active and/or are regulated by phosphorylation-dependent changes, by the activity of lipid second messengers such as phospholipases, or may even have nucleotide-exchange independent regulation. Regardless of these deviations from the established norm, the biochemical properties of plant G-proteins are key to affecting plant phenotypes and responses. Detailed characterization of such activities, in vitro and in planta, will pave the way for precise manipulation of these proteins for future agricultural needs.
Keywords: G-proteins; GAP activity; GTP-binding; GTPase activity; Heterotrimeric G-proteins; PLDα1; Phosphorylation; Plants; RGS1; RLKs.
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